From: John Beckett 

"Geo."  wrote in message
news::
> Ok fine, prove humans are alive. I mean you guys seem to think there is some
> clear test for live, well ok so spell it out. I spelled out mine, all life
> has it's own DNA and anything that isn't alive has no DNA. That's pretty
> simple test for life.
>
> So what's yours? Adam seems to think something has to breath to be alive, I
> find that to be reasonable but I don't know if single cell creatures breath,
> I don't think they do but I'm open minded on it.

I've been saying this is a semantic issue for some time now. Obviously, the
question "are viruses alive" first requires a definition of
"alive".

Re your definition that something is alive if it has DNA: The evolution of
life from inanimate matter is a very unlikely event. The fact that all
living matter uses DNA (and has certain other key characteristics) suggests
that life has evolved only once on Earth.

So, I would say that your "life is DNA" definition is not
satisfactory. All life uses DNA merely because all life has a common
origin. The species we see have diverged from that common ancestor.

I won't try to define life, but I will suggest that a satisfactory
definition would include self reproduction. To me, viruses don't have self
reproduction and so are not alive.

John

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